Vaporization of single liquid drops in an immiscible liquid part II: Heat transfer characteristics
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Abstract
Heat transfer characteristics during the vaporization process of a pentane or furan drop in an aqueous glycerol of high viscosity has been studied. With the progress of vaporization, the overall heat transfer coefficient related to the liquid-liquid interfacial area of a two-phase bubble increases monotonically, and influences of initial drop diameter and temperature difference reduce. Some convection or circulation seems to occur in the unvaporized-liquid phase.
Keywords
Heat Transfer Convection Transfer Coefficient Heat Transfer Coefficient PentanNomenclature
- A
total surface area of two-phase bubble
- AL
liquid-liquid interfacial area of two-phase bubble
- D
equivalent spherical diamter of two-phase bubble
- Di
initial drop diameter
- h
average overall heat transfer coefficient related to A
- hc
average outside heat transfer coefficient related to A
- qθ
local outside heat transfer coefficient
- hL
average overall heat transfer coefficient related to AL
- hLc
average outside heat transfer coefficient related to AL
- kc
thermal conductivity of continuous-phase liquid
- kdl
thermal conductivity of dispersed-phase liquid
- kv
correction factor of velocity [cf. Eq.(2)]
- Nuc
=hc D/k
- Nucθ
=hcθ D/kc
- Pec
=UD/αc
- Prc
=νc/αc
- Q
cumulative heat transferred into two-phase bubble
- qθ
local heat flux
- r
radial distance in spherical co-ordinates
- R
radius of two-phase bubble
- T
temperature
- TL
interface temperature between continuousphase and dispersed-phase component in liquid phase
- T∞
bulk temperature
- ΔT
temperature difference
- ΔT∞
nominal temperature difference
- U
velocity of rise of two-phase bubble
- u′
velocity gradient in r direction [cf. Eq.(9)]
- ur
velocity component in r direction
- uθ
velocity component in θ direction
- V
volume of two-phase bubble
- Vdl
volume of dispersed-phase component in liquid phase
- X
defined in Eq.(7)
- Y
defined in Eq.(8)
- Z
defined in Eq.(12)
- αc
thermal diffusivity of continuous-phase liquid
- β
half opening angle of vapor phase in two-phase bubble
- δ
average thickness of dispersed-phase component in liquid phase [cf. Eq.(22)]
- θ
angle in spherical co-ordinates
- ξ
vaporization ratio
- τ
time
Verdampfung einzelner Flüssigkeitstropfen in einer nicht mischbaren Flüssigkeit. Teil II: Der Wärmeübergang
Zusammenfassung
In dieser Arbeit wird der Wärmeübergang während der Verdampfung von Pentan- und Furan-Tropfen in einer wässerigen Glyzerinlösung hoher Viskosität untersucht. Mit fortschreitender Verdampfung steigt der Wärmeübergangskoeffizient, bezogen auf die Grenzfläche flüssig-flüssig der zweiphasigen Blase monoton an, wobei Einflüsse des anfänglichen Tropfendurchmessers und der Temperaturdifferenz abnehmen. In der nichtverdampften Flüssigkeitsphase scheint Konvektion oder Zirkulation aufzutreten.
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Literature
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